Many types of portable computing devices, such as laptop, notebook or tablet computers, personal digital assistants (PDA's), handheld game devices and the like, use rechargeable batteries which require periodic connection to a source of power to replenish their energy stores. Typically, such devices include a power input port or jack which accepts a connector attached to a power source, such as the DC output of an external voltage converter connected to a an AC power outlet, or an automotive electrical system. A few portable computing devices are designed to directly accept AC line power, but generally this is not preferred insofar as it requires that a voltage converter be incorporated within the device, thereby increasing its size and weight. For the most part, use of an internal AC converter is avoided because small size and low weight are primary design goals to enhance device portability. In either case, the power input port is typically configured so that is can be used both as a source of power for operating the device and for recharging the device battery. While for convenience the present specification refers to a device battery, the present discussion and invention are equally applicable to devices with multiple batteries.
Generally, the external power connection is made via a male/female plug and receptacle combination. Specifically, in the typical arrangement a male element from the power source is inserted into a recess in the computing device with appropriate contacts to enable electrical connection. When DC power is being supplied to the portable computing device from an external power supply, the connector must be configured to ensure the correct voltage polarity.
Some types of known portable computing devices, such as PDA's and tablet computers are adapted to reside in a “cradle” which provides various types of connections to the device. Laptop, notebook and tablet computers may be adapted to be received in a “docking station” which provides various types of connections to the computer. By way of examples, a cradle used with a PDA may be connected to a personal computer to enable data synchronization, or a docking station may provide a plurality of “ports” for connecting various types of devices, such as printers, network and telephone lines, speakers, pointing devices, etc. to a laptop computer. Typically, the cradle or docking station has a specialized or proprietary plug-in type connector which supplies operating power to the device as well as providing the additional functionality, as described.
Known prior art cradles and docking stations use high density pin contacts to provide extensive functionality, but these high density connectors have limited life, especially when subjected to heavy use. Thus, while providing added functionality, prior art cradles and docking stations require the user to pay considerable attention to the operations of aligning and inserting the portable computing device into the connector to make connection. Often docking stations have a locking mechanism which requires the user to perform the additional step of locking the device for docking, and which requires the user to activate a release mechanism to disengage the device.
Tablet computers have found particular utility in field settings where portability, ease of use and computing power are important, but where use of a notebook or laptop may not be practical. Exemplary settings where tablets computer are particularly useful include law enforcement, delivery services and health care. Often, in such settings, a large number of tablet computers are subject to heavy use requiring frequent recharging. In such settings, ease of use is particularly important. In addition to the portability they afford, tablet computers are typically adapted for use with docking stations, enabling them to have the full functionality of a personal computer. However, in many settings the need for frequent recharging is greater than the need for full functionality and so recharging through a docking station is unnecessary and inconvenient.